Method and device for detecting the contour data and/or optical characteristics of a three-dimensional semi-transparent object

ABSTRACT

A method and device for detecting the contour data and/or optical characteristics of an object, such as a tooth or a tooth restoration, based on an interference and/or autocorrelation measurement using an image sensor. To permit an exact surface detection in addition to a determination of the optical characteristics of the object, individual light beams strike the object, which are located at a distance from one another in such a way that no impact of reflected individual light beams takes place on immediately adjacent pixels of the image sensor.

The invention relates to a method for recording contour data and/oroptical properties of a three-dimensional semi-transparent object,especially a semi-transparent object in the dental area, such as a toothor tooth restoration, on the basis of an interference and/orautocorrelation measurement, whereby

-   -   a bundle of rays from at least one light source of short        coherence length is generated,    -   the bundle of rays is passed through a beam splitter and is        preferably guided to the object through a focusing optical        system,    -   a reference beam is split off in the beam splitter from the        bundle of rays and is reflected by a reference mirror movable        along the reference beam, whereby by moving the reference        mirror, a position relative to a signal gaining surface is fixed        relative to the object, and    -   the beam reflected from the object and from the reference mirror        are brought together in the beam splitter and transferred into        an image sensor having pixels, whereby temporally and/or        spatially altered signal patterns can be recorded upon passing        through the signal recovering surface.

Furthermore, the invention makes reference to a device for recordingcontour data and/or optical properties of a three-dimensionalsemi-transparent object, especially a semi-transparent object in thedental area such as a tooth or tooth restoration, including at least onelight source of short coherence length for generating a bundle of rays,a radiation component guiding the bundle of rays to the object through afocusing optical system on the one hand, and on the other into a beamsplitter splitting up into a beam component leading to an adjustablereference mirror as well as an image sensor having pixels, which can beacted upon by the object and radiation reflected from the referencemirror and the beam splitter.

A method of the aforementioned type is described in German PatentDE-A-43 09 056, for example. With the known process, it is a matter ofan interferometric method for ascertaining the distance and thescattering intensity of scattering points. These are illuminated by abroad band, spatially partially coherent light source and are located inone arm of an interferometer. An incandescent lamp or a superluminescence diode are indicated as light source. The light is separatedinto a spectrum and the output of the interferometer and information onthe distance and the scattering intensity is ascertained on the basis ofthe brightness distribution in the spectrum. The disadvantage with thedescribed method is that the resolution in the z direction, that is,into the depth of the object, is restricted.

In the article by Prof. G. Häsler: ““COHERENCE RADAR”—an Optical 3DSensor with an Exactitude of 1 μm,” LASER INFO EXCHANGE, No. 36/April1999, Association of German Engineers Technology Center, a method and adevice for measuring a surface are described. The measuring principlerests upon white light interferometry, whereby local speckles aregenerated by a particular illumination selectively so that even the mostdistinct optically raw objects, such as milled surfaces or rubber, canbe measured interferometrically. According to the method, one basicallycompares the length of the path of light for each object point with thelength of the corresponding reference path of the interferometer. Onlywhen the path lengths are approximately equal does an informationcontrast arise in the corresponding image point. While the sensor ismoving toward the object, the point in time of the maximal interferencecontrast is determined individually for each image point and therespective sensor position is stored in memory.

A method and a device are known from German Patent DE-A-40 34 007,whereby the coating of the object is provided for obtainingthree-dimensional data to avoid disturbing scattered radiation from thedepth of a semi-transparent object such as, for example, a tooth or adental filling which prevents this scattered radiation. This layer mustnonetheless be applied by the dentist. This is thus an additionaloperation, which moreover can lead to irritations of the patient'srespiratory passages due to the aspiration of dust articles in the eventlarge areas of the dental corona are powdered. In US Patent U.S. Pat.No. B-6,697,164, a method and device are described, whereby theinfluence of a scatter beam is reduced through a confocal opticalsystem. With this method, an array of incident light rays is guided intoan optical beam path which is guided though a focusing optical system toa test surface. The focusing optical system defines one or more focalplanes in front of the test surface in a position which can be changedby the optical system, whereby each light ray has its focus in referenceto one or more focal planes. The rays generate a manifold of light spotson the contour. The intensity of each of these light spots is recorded.The steps mentioned above are repeated several times, whereby each timethe position of the focal plane is altered relative to the contour. Alight-point specific position is determined for each of the light spotswhich corresponds to a position of the respective focal plane whichleads to a maximal measured intensity of a respective reflected lightray. Data are generated on the basis of the light spot-specificpositions which represent the topology of the contour.

The described device for recording a surface topology of a region of athree-dimensional structure includes a probe with a contour to bescanned. Furthermore, a light source for generating an array of incidentlight rays which is transferred to the structure along an opticalpathway is provided in order to generate light spots on the region. Alight-focusing optical system defines one or more focal planes beforethe sample structure in a position which can be altered by the opticalsystem. Each light ray has its focus on one or more focal planes.Furthermore, a displacement mechanism is linked with the focusingoptical system in order to move this relative to the structure along theaxis which is defined by the incident light rays. Moreover, a detectoris provided with an array of sensor elements for measurement of theintensity of each of a large number of light rays which are reflectedfrom the light spots opposite to the incident light. A processor islinked with the detector in order to ascertain a light spot-specificposition for each light ray. Since a reflected light ray reaches themaximal intensity when the reflection position is situated in the focalplane, its specific position can be ascertained therewith. Data on thetopology of the region are generated on the basis of the ascertainedlight spot-specific positions.

The influence of scattered radiation can be significantly reduced byusing a confocal optical system from the aforementioned U.S. Pat. No.6,697,194 B1.

A process and a device for measuring the contour data of an object canbe derived from WO-A-95/33971. Here the interferometer principle isused, whereby a light source of coherence length is used. In order tosubject the object to the action of light in sufficient spatialextension, there exists the possibility of expanding the lightoriginating from a light source. The light rays running in the bundle ofrays are nonetheless not separated from one another, but in part overlapone another.

A method for measuring dimensionings or optical properties of biologicalsamples is known from U.S. Pat. No. 5,321,501, whereby theinterferometer principle is likewise used. According to one embodiment,rapidly changing biological samples can be acted upon with radiationfrom different optical sources at the same time. Each ray source isallocated a detector. Several regions of the sample can be scannedparallel and simultaneously.

The present invention is based upon the objective of further developinga method and a device of the type mentioned in the beginning, such thatan exact surface recording and an ascertainment of the opticalproperties in the desired extent can take place. At the same time, anadaptation to the conditions of the shape of the object and the opticalproperties should take place in so far as the rays can be adjusted tothe desired extent.

As regards the method, the objective is accomplished in that the bundleof rays is being or is divided before impingement upon the beam splitterinto spatially distanced parallel individual light rays, whereby theindividual light rays have a spacing from one another such that animpingement of reflected individual light rays on immediately adjacentpixels of the image center does not occur. The scattered radiationgenerated by a semi-transparent object is detected with the remainingpixels which are not illuminated by individual rays.

While according to German Patent DE-A-43 09 056, the object isirradiated with a continuous illumination that is irradiated with anon-interrupted, uniform bundle of rays, owing to which an expensiveevaluation is necessary, according to the invention, operations takeplace with a raster of spaced light rays. That is, with a bundle of raysof parallel light rays so that scatterings inside the object to bemeasured are detectable between the reflecting rays and the adjacentrays are not influenced. Here is it especially proved that the spacingof the individual light rays is adjusted such that two immediatelyadjacent individual light rays impinge upon pixels or pixel regionsbetween which at least one pixel, preferably at least two to fivepixels, are not acted upon directly by a reflected light ray.

Consequently, it is provided in accordance with the invention that eachpixel illuminated by a reflected individual light ray or eachcorrespondingly illuminated pixel group is surrounded by a primarilynon-illuminated region, which once again can be illuminated in the eventof scattered light. Regardless of this, this region acted upon byscattered light is designated as a pixel or pixel region not acted uponby an individual light ray.

Consequently, an exceedingly precise recording of the contour of theobject to be measured is possible on the basis of the theory of theinvention, whereby it can not only be a question of solid object, butcan also be a matter of flexible objects, such as, for example, themucosa.

It can be a matter of white light with the light source. Alternatively,the light can also be generated from at least one super luminescentdiode or an array of single or several super luminescent diodes or atleast one broad band high performance light diode or an array of singleor several relatively broad banded high performance light diodes.Likewise, the combination of several laser diodes with central wavelengths offset in relation to one another is possible, whereby a wavelength shift can lie in the range of 5 nm to 150 nm, preferably in therange from 10 nm to 50 nm.

Preferably the coherence length l_(c) of the light source used lies inthe range of 2≦l_(c)≦20 μm, with an emission output P_(E) of the lightsources in the range of 1≦P_(E)≦100 mW, preferably 3≦P_(E)≦50 mW.

In deviation from the state of the art, according to the method of theinvention, surface as well as depth information can be obtained, and tobe sure through selection of the suitable wave length in which thescattering coefficient of the object is correspondingly high or low.With measurements with light in near infrared, the scattering becomesless, since this decreases with increasing wave length.

It is provided in accordance with a preferred procedure that light ofshort coherence length of a single or several light sources be expandedthough a beam expander and projected onto an array of lenses whichgenerates a large number of parallel individual rays. The lens array canhave a large number of lenses arranged like a honeycomb, through whichthe impinging bundle of rays is subdivided into the desired individuallight rays running spaced and parallel to one another. The parallellight rays run through a beam splitter, a beam shifter and through anaxially displaceable focusing optical system to the object whosegeometrical data are to be measured. The beam shifter serves to shiftthe bundle of rays by fractions of the distance between the individualrays in order thus to heighten the resolution.

In a preferred embodiment, the beam shifter is constructed as a planarplate, which can be slightly tilted perpendicular to the ray directionin the x and y direction. A reference beam is split up in the beamsplitter and reflected on a reference mirror. The reference mirror isarranged displaceable in the direction of the ray, thus in the axialdirection, and establishes a signal recovering surface with the lengthof a reference arm, ideally a plane in one measuring arm of theinterferometer. This can be identical with the focusing plane of thefocusing optical system, but can also be different from this in order toobtain further information on the scattering behavior of thesemi-transparent object for subsequent image processing.

The individual light rays reflected by the object and the referencemirror are brought together in the beam splitter and overlapped in thedetector. If the path length differences of the reference arm and themeasuring arm lie in the region of the coherence length of the lightsource used, maxima and minima are shown during axial motion of thereference arm mirror.

The same technical possibilities exist with a multiplanar wave guidingelement as beam splitter.

In accordance with an alternative embodiment, the large number ofindividual rays can be generated directly in a VCSEL array (verticalcavity surface emitting laser). This has the advantage of individualaddressability of the individual rays.

An extension of the method of the invention provides that the rayguidance can also be realized by dispersion-poor monomodal fiber bundle.Here the light source is launched into a large number of parallel guidedfibers following expansion. The decoupling likewise takes place througha focusing optical system. The functions of the beam splitter take overthe fiber coupler in this case.

A differential measurement can be conducted with at least two differentwave lengths. These measurements can be conducted in accordance with theinvention with wave lengths in which the semi-transparent object in eachcase has a very different scatter and absorption coefficient in order tocompile a differential image on the basis of it.

To improve the signal-disturb signal ratio, it is provided that a largenumber of frames, that is, the overall image content of the image sensorof a defined period of time (sampling time), is filed in the memory ofan image processing computer attached to the image sensor and clearedwith one another during the traverse of the reference arm.

A device of the type mentioned at the beginning, through which theobjective underlying the invention is accomplished is distinguished inthat an optical element subdividing the bundle of rays into spatiallydistanced parallel single light rays is arranged between the lightsource and the beam splitter or the light source of the bundle of raysconsisting of a large number of parallel individual light rays isconstructed, whereby the individual light rays have a spacing from oneanother such that the impingement of reflected individual light rays onpixels of the image sensor directly bordering upon one another does notoccur.

Refinements Result from the Dependent Claims.

In accordance with the invention, a method or a device for recordingoptical and geometrical properties of three-dimensional,semi-transparent objects, especially of the dental region, such asteeth, composite materials, veneer ceramics through the use of aninterference and/or auto-correlation measurement with at least one lightsource of short coherence length is proposed, which is distinguished bythe following features or groups of features:

-   -   A raster of defined spaced light rays, that is, a bundle of rays        of parallel light rays, is used so that scatterings inside the        object to be measured are detectable between the reflected rays,        and the neighboring rays are not influenced,    -   At the same time, at the image sensor, only one subset of        available pixels is directly illuminated by a corresponding        light ray (at least one un-illuminated pixel interval between        the illuminated pixels). Around each illuminated pixel or each        pixel group (in the event that a light spot simultaneously        illuminates several pixels lying alongside one another), there        is located a primarily non-illuminated region which nonetheless        in the event of the impingement of scattered light (in the        semi-transparent object) is also illuminated,    -   A beam shifter is used to shift the bundle of rays by fractions        of the spacing of the individual rays in order to increase the        exactitude of the method by a large number of measurements        displaced in relation to one another. Preferred embodiment of        the beam shifter: plane parallel plate which is easily tilted. A        displacement takes place between the frames by fractions of the        distance of the illumination rays,    -   A combination of various laser diodes with offset central wave        length is used, whereby a wave length offset can lie from 5 nm        to 150 nm, preferably in the range from 10 to 50 nm,    -   Through suitable choice of the wave length at which the        scattering coefficient of the object is correspondingly high or        low, depth or surface information can be obtained,    -   A differential measurement of at least two different wavelengths        can be conducted in which the semi-transparent object in each        case has a very different scatter and absorption behavior in        order to generate a differential image,    -   When using the spectral range in the near-infrared, for example        750 nm to 1000 nm, available depth information can then also be        used for caries diagnosis,    -   In the event that two or more wave lengths are used        simultaneously, an RGB variant of a CMOS sensor can be used        which has sensitivity maxima in the red, green and blue spectral        region,    -   The signal recovering surface (plane with maximal interference        contrast) can be identical with the focal plane, but can also be        different from this in order to obtain further information on        the scatter behavior of the semi-transparent object for        subsequent image processing,    -   In accordance with an alternative embodiment, a large number of        individual rays can be generated directly in a VCSEL array. This        has the advantage of individual addressability of the individual        rays,    -   A launching of light into a large number of individual fibers        can assume the function of the beam splitter.

Further particularities, advantages and features of the invention becomeapparent not only from the claims, the features to be inferred fromthese—by themselves and/or in combination—but also from the subsequentdescription of the embodiments to be derived from the drawings. Featuresand feature combinations of the subsequently described embodiments arealso expressly maintained in this connection, wherein:

FIG. 1 Illustrates a basic construction of a device for recordingcontour data of an object,

FIG. 2 Is a schematic diagram for clarification of the measuringprinciple,

FIG. 3 Illustrates coherence length of the light source as a function ofits central wave length,

FIG. 4 Illustrates the scattering coefficient of enamel and dentine as afunction of wave length,

FIG. 5 Illustrates the absorption coefficient of enamel and dentine as afunction of wave length,

FIG. 6 Is a schematic diagram of a further arrangement for recordingcontour data of an object,

FIG. 7 Is a schematic diagram of a sensor housing and

FIG. 8 Illustrates the underside of the sensor housing in accordancewith FIG. 7.

FIG. 1 illustrates a schematic construction of a device 10 for recordingcontour data of a free form surface 12 of a semi-transparent object 14.

The light of a light surface 16 of short coherence length is expandedthrough a beam expander 18 and projected on a lens array 20 whichgenerates from this a bundle of rays 22 of a large number of individualrays. These run through a beam shifter 26, a beam splitter 24 andthrough an axially displaceable focusing optical system 28 to the object14, such as a tooth, whose geometrical data are to be measured.

The beam shifter 26 serves to shift the bundle of rays 22 by fractionsof the distance between the individual rays in order to increase theresolution. In this way, there exists the possibility of shifting thebundle of rays 22, that is its individual light rays overall, withrespect to place in order consequently to be able to measure the regionsof the object 14 as well which possibly could not be recorded by otherimpingement points of individual light rays.

The beam shifter 26 can, for example, be constructed as a plane parallelplate which can be slightly tilted perpendicular to the ray direction inx and y.

A reference ray 30 is split in the beam splitter 24 and reflected on areference mirror 32. The reference mirror 32 is arranged displaceable inthe direction of the reference ray 30, thus in an axial direction inaccordance with arrow 34 and establishes with the length L of areference arm 36 a signal recovering surface 38, ideally a plane, in ameasuring arm 40 of an interferometer.

This can be identical with a focal plane of the focusing optical system28, but can also be different from this in order to obtain furtherinformation on the scatter behavior of the semi-transparent object 14for subsequent image processing. On the return path of the object 14,the individual light rays reflected from the object 14 and theindividual light rays reflected from the reference mirror 32, thus bothlight paths, are brought together in the beam splitter and overlapped inan image sensor 42.

The signal recovering surface 38 is the plane with maximal interferencecontrast or should be this.

If the path length difference of the reference arm 36 and the measuringarm 40 lie in the range of the coherence length of the light source 16used, minima and maxima are shown on the image sensor 42 upon axialmovement of the reference arm mirror 32.

FIG. 2 shows a raster-like distribution of the illumination points 44 onthe measured object 14 as well as on the image sensor 42. At the sametime, only a subset 46, 47 of available pixels 48 is directlyilluminated on the image sensor by a corresponding light ray 43, 45. Ashifting of the raster takes place between the frames by fractions ofthe spacing of the illumination rays.

A large number of parallel individual rays 43, 45 (illumination raster)are correspondingly thus illustrated centered on respectively one or fewpixels 46, 47 of the image sensor 42. Around each illuminated pixel 46,47 or each pixel group, there is located a primary non-illuminatedregion (for example, pixel 49) which is nonetheless illuminated in theevent of the impingement of scattered light which is the normal casewith a semi-transparent object. The signal-disturb signal ratio istherewith worsened.

In order nonetheless to be able to obtain three-dimensional data on thesurface 12 of object 14, a large number of frames, that is, the entireimage content of the image sensor 42 of a defined period of time(sampling time) are filed in the memory of an image processing computerconnected to the image sensor 42 during the traverse of the referencearm 36.

If one knows a position of the reference arm 36 in which definitively nomeasuring signal of the objects 14 can be present (for example, in theshortest position of the reference arm at which the measuring plane 38lies close above the object 14), one can proceed from the assumptionthat residual signals, which nonetheless occur, are disturb signals andcan be classified as such. If one moves the signal recovering surface 38by displacing the reference mirror 32 further in the direction of themeasured object 14, at some time there arises a point of intersection ora line of intersection or if need be also a surface of intersectionbetween the signal recovering surface 38 and the object contour 12. Thencharacteristic intensity fluctuations which express changing imagepatterns from frame to frame on the corresponding pixels of the imagesensor 42 occur in reference to the corresponding pixels of the imagesensor. The rather static intensity distributions can in contrast berestricted in connection with the method. Hence a brightness patternsensor can be built up when the signal recovering surface is passedthrough by the measured object by linking the temporo-spatial signalpattern of the consecutive frame.

A priori knowledge in the form of a data base is used for surfacecontour data extraction which contain typical combinations from scatter,absorption and anisotropy factors of the corresponding semi-transparentmaterial. The scattered light distribution to be expected is calculatedin this way. A calculation method which describes the optical propertiesof semi-transparent tissues is, for example, described in thedissertation of Weniger K., Free University of Berlin, 2004.

Likewise, to the extent that the contour to be expected is known, thuscapable of being allocated to a specific contour class, this can be usedto provide data with priorities. The sequence of measurement is guidedby a microcontrol unit. This entails shifting the focusing opticalsystem and the reference arm mirror as well as motion of the beamshifter.

3D contour data, which are received partially overlapping from variouspositions of the image sensor are combined using software toward anoverall dataset.

An STL file is compiled on the basis of the extracted contour data ofthe measured object which can be further processed with suitable CAD/CAMsystems.

The present invention describes a device and a method for recovery of 3D data of semi-transparent objects by using interferencemeasurements/auto-correlation measurements with light sources of shortcoherence length. This can be white light in the extreme case, but alsooriginate from one superluminescent diode or an array of them, or fromone relatively broad-banded high performance light diode or from anarray of several of them. Likewise, a combination of several laserdiodes with central wave lengths offset in relation to one another ispossible. The wavelength offset can amount to 5-150 nm, preferably 10-50nm.

The coherence length l_(c), which is determinative for the longitudinalresolution of an OCT (Optical Coherence Tomography) measurement, existsfor a Gaussian spectral distribution by:

$l_{c} = {\frac{2\; \ln \; 2}{\pi}\frac{\lambda^{2}}{\Delta \; \lambda}}$

The coherence length should lie preferably in the 2-20 μm range, withemission outputs in the range from 1 to 100 mW, preferably 3-50 mW. Aconnection between the central wave length and the band width (FWHM) ofthe light source is represented in FIG. 3.

Deviating from the state of the art, only surface information is to berecovered in the described method. Therefore light sources withwavelengths in which the scattering coefficient of the object is highcan also be selected. In this way, a differential measurement of atleast two different wave lengths is possible.

In accordance with the invention, these can also be two measurementswith wave lengths at which the semi-transparent object 14 in each casehas very different scatter and absorption coefficients to compile adifferential image from them.

In the event of a high scattering coefficient, a small but brightscatter halo will then form in the near field of the illumination point.In the event of a small scattering coefficient, the scattered light willspread wide in the semi-transparent medium but will have a lowerintensity in the near field. This opens extended evaluationpossibilities through image processing software.

In the case of tooth hard substance, one wave length range with a highscattering coefficient lies in the blue and ultraviolet spectral range,whereby wave lengths under 350 nm should be avoided due to the danger ofthe induction of DNA strand breaks and radical formation. The scatteringcoefficient lies in the case of dental hard substance in the 8-90 l/mmrange with absorption coefficients in the 0.1-1.5 l/mm range. Withdental filler material, the scattering coefficient lies here in the 8-25l/mm range and the absorption coefficient at 0.3-4 l/mm.

Wave length ranges of low scatter for semi-transparent objects incontrast lie in the red and infrared spectral ranges. For dental hardsubstance, the scattering coefficient lies in the 1-40 l/mm range fordental enamel at the lower boundary and for dentine in the upper range.Filler materials lie in the 3-20 l/mm range. Examples for scatter andabsorption coefficients for enamel and dentine can be gathered from FIG.4 and 5.

The diminishing spectral sensitivity of the detector is limiting in thenear infrared. In the case of a preferred embodiment, this falls at 1000nm under 5% with a CMOS sensor. The use of a CCD sensor is likewisepossible. Furthermore the wave length range can be extended into theinfrared with suitable sensors. InAs or HgCd Te detectors, for exampleare suitable for this with which the 2.5-10 μm range can be covered.

In case the spectral range of the near infrared, for example 750 nm to1000 nm, is being used, the depth information then available can also beused for caries diagnosis. In the event that two or more wave lengthsare to be used simultaneously, an RGB variant of a CMOS sensor can beused, which has sensitivity maxima in the red, green and blue spectralrange.

FIG. 6 shows a schematic diagram of an alternative embodiment of adevice 50 for recording contour data of three-dimensional objects,whereby like elements are characterized with the same reference numbers.In extension of the device 10 in accordance with FIG. 1, a trackingdevice 52 is provided which makes possible an axial change in length ofthe reference arm 36 when shifting the focusing lens 28 along arrow 54.Deflection mirrors 56 are arranged in the tracking device 52 for thispurpose. A further deflection mirror 58 is arranged in lengthening thelight ray exiting from the beam splitter 24 in order to attain adeflection of the light ray on the mirror arrangement 56 arranged in thetracking device. In order nonetheless with this device to make possiblea separation of the focal plane of the signal recovering plane, themirror 32 can preferably be shifted axially separated in the directionof arrow 60.

FIG. 7 depicts an outer contour of a sensor housing 62 for use indentistry for intraoral scanning of teeth. In order to make possible acomfortable operation in the month of a patient, the dimensions must beoriented around the anatomy of the patient. A wedge-shaped arrangementis a preferred embodiment.

FIG. 8 shows an underside 64 of the sensor housing 62 in which a scanwindow 66 is arranged. The length of the scan window 66 makes possible asimultaneous recording of a quadrant.

1. Method for recording contour data and/or optical properties of athree-dimensional, semi-transparent object (14), especially asemi-transparent object in the dental area, such as a tooth or toothrestoration, on the basis of an interference and/or auto-correlationmeasurement, whereby a bundle of rays (22) from at least one lightsource (16) of short coherence length is generated, the bundle of raysis passed through a beam splitter (24) and is preferably guided to theobject (14) through a focusing optical system (28), a reference beam(30) is split off in the beam splitter from the bundle of rays and isreflected by a reference mirror (32) movable along the reference beam,whereby by moving the reference mirror, a position relative to a signalrecovering surface (38) is fixed relative to the object (14), and thebeam reflected from the object and from the reference mirror are broughttogether in the beam splitter and transferred into an image sensor (42)having pixels (46, 47, 49), whereby temporally and/or spatially alteredsignal patterns can be recorded upon passing through the signalrecovering surface, wherein the bundle of rays (22) is being or issubdivided before impinging upon the beam splitter (24) in spatiallydistanced parallel single light rays (43, 45), whereby the individuallight rays have a spacing in relation to one another such that animpingement of reflected individual light rays on immediately boundingpixels (46, 49) of the image sensor (42) does not occur.
 2. Methodaccording to claim 1, wherein the spacing of individual light rays (43,45) is adjusted such that two directly adjacent individual light raysimpinge upon pixels (46, 47) or pixel regions between which at least onepixel, preferably 2 to 5 pixels are not acted upon directly by areflected individual light ray.
 3. Method according to claim 1, whereina differential measurement with at least two different wave lengths isconducted to determine the contour or the optical properties of theobject (14) in which the object in each case has different scatter andabsorption coefficients.
 4. Method according to claim 1, wherein a lightsource (16) with a coherence length l_(c) in the range of 2 μm≦l_(c)≦20μm at an emission output P_(E) of the light source in the range of 1mW≦P_(E)≦100 mW, preferably 3 mW≦P_(E)≦50 mW is used.
 5. Methodaccording to claim 1, wherein white light and/or at least asuperluminescent diode and/or an array of superluminescent diodes and/orat least one broad band high performance diode and/or an array ofseveral broad banded high performance diodes is used as the light source(16).
 6. Method according to claim 1, wherein the light of shortcoherence length, especially when using a single light source or a smallnumber of light sources (16), is expanded through a beam expander (18)and projected on a lens array (20) to generate a bundle of rays having alarge number of parallel single light rays.
 7. Method according to claim1, wherein the large number of single rays is generated directly in aVCSEL array.
 8. Method according to claim 1, wherein a combination ofseveral laser diodes with central wave lengths offset in relation to oneanother is used as a light source, whereby a wave length offset Δλ liesin the range 5 nm≦Δλ≦150 nm, preferably 10 nm≦Δλ≦nm.
 9. Method accordingto claim 1, wherein a large number image contents (single patterns) ofthe image center recorded during a period of time (sampling period) ofthe image sensor are filed in the memory of an image processing computerand cleared with one another.
 10. Method according to claim 1, whereinthe bundle of rays (22) is shifted using a beam shifter (26) byfractions of the spading between two single rays.
 11. Method accordingto claim 1, wherein the beam shifter (26) constructed as plane parallelplate is slightly tilted perpendicular to the ray direction in the X andY direction.
 12. Method according to claim 1, wherein a CMOS sensor isused as the image sensor (42).
 13. Method according to claim 1, whereina CCD sensor is used as an image sensor (42).
 14. Method according toclaim 1, wherein InAs or HgCdTe detectors are used as sensors. 15.Method according to claim 1, wherein a light source (16) emitting in thespectral range of the near infrared, preferably between 700 nm-1000 nmis used.
 16. Method according to claim 1, wherein an RGB variant of aCMOS sensor is used for simultaneous use of two or more wavelengths oflight rays, whereby the depth information then available is also usedfor caries diagnosis.
 17. Method according to claim 1, wherein the rayguidance takes place through a dispersion-poor monomodal fiber bundle,whereby the light of the light source is launched following expansioninto a large number of parallel guided fibers and is decoupled through afocusing optical system.
 18. Method according to claim 1, wherein apriori knowledge in the form of typical combinations of scatter,absorption and anisotropy factors for the corresponding semi-transparentmaterials is used for surface contour data extraction.
 19. Methodaccording to claim 1, wherein the data ascertained on the basis ofcontour classes are evaluated (weighted) for objects to be scannedand/or provided with a priority.
 20. Method according to claim 1,wherein the signal recovering surface (38) (plane with maximalinterference contrast) is adjusted agreeing with the focal plane of thefocusing optical system (28).
 21. Method according to claim 1, whereinthe signal recovering surface (38) for recovering further information onthe scatter behavior of the semi-transparent object (24) for subsequentimage processing deviates from the focal plane generated by the focusingoptical system (28).
 22. Method according to claim 1, wherein scatteredradiation is detected by pixels (49) not directly illuminated by singlelight rays (43, 45) which originates from the semi-transparent object(14).
 23. Device for recording contour data and/or optical properties ofa three-dimensional, semi-transparent object (14), especially asemi-transparent object in the dental area such as a tooth or toothrestoration, including at least one light source (16) of short coherencelength for generating a bundle of rays (22), a beam splitter (24)splitting the bundle of rays first into a radiation component leading tothe object through a focusing optical system (28) and secondly into aradiation component leading to an adjustable reference mirror (32), aswell as an image sensor (42) having a pixel (46, 47), which can be actedupon by radiation from the object and reflected from the referencemirror and brought together by the beam splitter, wherein an opticalelement (20) subdividing bundle of rays (22) into spatially distancedparallel single light rays (43, 45) is arranged between the light source(16) and the beam splitter (24), or the light source (16) is constructedfor generating the bundle of rays (22) consisting of a large number ofparallel single light rays, whereby the single light rays have a spacingfrom one another such that an impingement of reflected single light rayson pixels (46, 49) of the image sensor directly bordering on one anotherdoes not occur.
 24. Device according to claim 23, wherein the lightsource (16) has a single light source or several light sources, wherebya beam expander (18) for expanding the bundle of rays (22) and a lensarray (20) for generating the bundle of rays (22) having severalparallel light rays is arranged downstream in series from the individuallight source or the light sources.
 25. Device according to claim 23,wherein a beam shifter (26) is arranged in the ray path of the bundle ofrays (22) in front of the beam splitter (24).
 26. Device according toclaim 25, wherein the beam shifter (26) is constructed as a planeparallel plate which can be slightly tilted perpendicular to the raydirection in the X and Y direction.
 27. Device according to claim 23,wherein the light source (16) is a light source generating white light.28. Device according to claim 23, wherein the light source (16) is asuperluminescent diode or an array of superluminescent diodes. 29.Device according to claim 23, wherein the light source (16) is a highperformance light diode or an array of several relatively broad bandedhigh performance light diodes.
 30. Device according to claim 23, whereinthe light source (16) is a combination of several laser diodes withoffset central wave length in relation to one another, whereby the wavelength offset Δλ runs in the 5 nm≦Δλ<150 nm range, preferably 10nm≦Δλ≦50 nm.
 31. Device according to claim 23, wherein the coherencelength of the light source (16) lies in the region of 2 μm≦L_(C)≦20 μmat an emission output P_(E) of the light source in the region of 1mW≦P_(E)≦100 mW, preferably 3 mW≦P_(E)≦50 mW.
 32. Device according toclaim 23, wherein the light source (16) is constructed as a VCSEL array.33. Device according to claim 23, wherein the device has a trackingdevice (52) which makes possible a simultaneous axial change in lengthof the reference arm (36), a spacing change between the reference mirror(32) and the beam splitter (24) when shifting the focusing lens (28).34. Device according to claim 23, wherein a mirror arrangement (56) isprovided in the tracking device for deflecting the reference beam. 35.Device according to claim 23, wherein the beam expander (18) isconnected with the beam splitter (24) constructed as fiber couplerthrough a large number of parallel guided fibers such as dispersion-poormonomodal bundles.
 36. Device according to claim 23, wherein the beamsplitter (24) is constructed as a multiplanar wave guide element. 37.Device according to claim 23, wherein focal planes generated by thefocusing optical system (28) agrees with a signal recovering surface(38) (plane with maximal interference contrast) generated by theradiation reflected by the reference mirror (32) or deviates from it.